Quick Answer: Water expands roughly 9% when it freezes, with enough force to split PVC, crack poly fittings, destroy valve diaphragms and fracture a backflow preventer body. In New Jersey’s Zone 7a/7b climate, an un-winterized system will almost always sustain damage — and the repair bill reliably exceeds the cost of the blow-out that would have prevented it. Book winterization for the October 15 – November 15 window.
The Physics, Briefly
Water is unusual: it expands as it freezes rather than contracting. That expansion generates enormous force inside a sealed pipe — more than enough to exceed the burst rating of irrigation-grade PVC and poly. Your pipes do not stretch. Something gives.
And it does not require a brutal winter. Ground temperatures at the Jersey Shore drop below freezing from late November into February most years. One hard freeze on a system holding water is sufficient.
What Actually Breaks, in Order of Cost
1. The backflow preventer — the expensive one
This is the device that keeps irrigation water from flowing back into your drinking supply. It is required by New Jersey law, it sits above ground, and it is the most freeze-exposed component on the entire system. The brass or bronze body cracks, and cracked bodies are not repairable — the unit gets replaced. This is consistently the single largest line item on a spring freeze-damage invoice.
2. Valve manifold and solenoid valves
Valve bodies hold water. Freeze cracks the body or ruptures the internal diaphragm. A cracked manifold usually means digging up and rebuilding the whole assembly, not swapping one part.
3. Underground lateral lines
Split laterals are the sneaky ones. You will not know until you pressurize the system in spring and find a section of lawn turning into a bog. Repair means locating the break and excavating — and on a long run, locating it is most of the labor.
4. Sprinkler heads
Water trapped in the head body freezes and cracks the housing or destroys the internal seal. Individually cheap. Across 40 heads, not cheap.
5. The pump, on well-fed systems
If you irrigate off a private well, the pump and its supply line hold water that a standard shutdown never touches. A frozen pump housing is a serious repair.
Why “I Just Drained It” Usually Isn’t Enough
Manual and automatic drain valves help. They do not finish the job. Irrigation lines are not laid perfectly level — they follow grade, they dip around roots and rock, and water settles in every low spot gravity cannot reach. Those pockets are exactly where the splits happen.
A compressed-air blow-out is the only method that clears water from the sections drains cannot reach. That is the whole reason the service exists.
The Part That Costs You Twice
Freeze damage is not discovered in January. It is discovered in April, when you turn the system on and half of it fails. Now you are competing for a repair slot during the busiest six weeks of the irrigation year, your lawn is going without water while you wait, and the repair is significantly more disruptive than the blow-out would have been.
We assess and repair freeze damage as part of our spring startup service — but the honest advice is to not need it.
Does Homeowners Insurance Cover It?
Generally, no. Most policies treat freeze damage to an irrigation system as a maintenance failure rather than a covered peril, particularly when the system was left un-winterized. Check your specific policy, but do not plan around it covering you.
The Simple Version
A professional blow-out is inexpensive, takes under an hour on a typical residential system, and is the cheapest insurance available on a system that cost thousands to install. Skipping it saves you one line item this fall and costs you several next spring.
Related
- Sprinkler Blowout PSI & CFM: What Pressure Is Safe
- How to Winterize a Backflow Preventer
- Winterization & Blowout FAQ
Booking fall winterization across the Jersey Shore now. Call or text 609-548-5187 or see our winterization service.